Impellers for centrifugal fans



March 21, 1961 J. c. BUSQUET IMPELLERS FOR CENTRIFUGA L FANS Filed April 7, 1958 lllilllv |\\Il\l FIGJ JAN C BUSQUET INVNTOR Patented Mar. 21, 1961 MELLERS FOR CENTREFUGAL FANS Jan C. Busquet, Hengelo, Netherlands, assignor to Koninklijlse Machinefabriek Gebr. Stork 8: Co. N.V., Hengelo, Netherlands Filed Apr. 7, 1958, Ser. No. 726,793

Claims priority, application Netherlands May 10, 1957 1 Claim. (Cl. 230-437) This invention relates to an impeller for a centrifugal fan provided with hollow blades, which at their trailing end are provided with one or more discharge openings in their wall remote from the impeller axis for a pressure fluid entering the interior of the blade and having a pressure exceeding that of the fluid flowing through the impeller and reigning at the circumference of the impeller. Said openings being distributed along at least part of the width of the blade. With such an impeller the pressure fluid flowing out of the opening or openings in the blade wall forms at this end of the blade a shield, which will prevent the flow of the fluid from the pressure side at the trailing end of the blade to the low pressure side of the blade. The outflowing pressure fluid thereby performs the function of a pivotal trailing end of adjustable blades, so that when varying the supply of the pressure fluid also the output of the impeller is varied.

The invention has for its object to adapt the action of the discharge opening at the trailing end of the blades to the velocity of the fluid flowing along the blade surface. To this end according to the invention the width of the discharge opening at the inflow side of the impeller is larger than at the rear wall of the impeller, as it appeared that at the outlet end of the blades the velocity of the fluid entering the impeller is considerably large-r near the inflow side of the impeller than at the rear wall of the impeller.

In the accompanying drawing, which illustrates an embodiment of the impeller according to the invention:

Fig. 1 is a longitudinal sectional view of an impeller with part of the casing, the impeller being shown partly in side view.

Fig. 2 is a cross-section of the impeller taken on the line IlII of Fig. 1.

The impeller body shown in the drawing consists of a front plate 1 and a hollow back plate 2 and between said plates the hollow blades 3 are secured. The blades 3 at their trailing end are each provided with a slot 4, which at the front wall 1 of the impeller is the widest and the width of which gradually decreases towards the centre of the impeller. A hub 5 is secured to the back plate 2 and by means of said hub the impeller is secured to a shaft 6.

The cavity of the back wall 2 of the impeller is provided with blades 7 and said cavity through holes 8 is in communication with the cavities of the impeller blades 3.

When the fan is in operation the fluid through the suction mouth 9 enters the impeller and is deflected at the front wall 1 of the impeller in the direction of the arrow a, so that the velocity of the fluid at the inlet edge of the blades at the front wall 1 will be the largest. The blades 7 draw the fluid in the vicinity of the impeller shaft 6 from the space bounded by the wall 10, so that the fluid with increased pressure flows through the apertures 8 into the impeller blades 3 and flows out through the slot 4 at the trailing end of the blades.

The slot 4 may also extend along the whole Width of the blade and need not end in a point, but may still have a certain width near the backplate 2 of the impeller, said width, however, being smaller than at the front plate 1. The slot 4 may also have a uniform width but should then extend only along part of the width of the blade e.g. along half the width. The slot may also be replaced by a number of holes which towards the back plate 2 of the impeller have a smaller area than the holes at the front plate of the impeller.

What I claim is:

An impeller for a centrifugal fan comprising a front plate, a back plate, hollow blades having leading and trailing ends and extending between said plates, an opening in one of said plates for each hollow blade and communicating with the interior of said blade, means for introducing fluid through said openings and into the blades at a pressure exceeding that existing at the periphery of the impeller when it is operating, a discharge opening at the trailing end in the wall of each blade adjacent the front plate and remote from the impeller axis, said opening extending for at least part of the width of the blade, the width of the discharge opening of the blade at the front plate of the impeller being larger than towards the back plate of the impeller.

References Cited in the file of this patent UNITED STATES PATENTS 390,508 Mosher et a1. Oct. 2, 1888 2,305,226 Stalker Dec. 15, 1942 2,476,002 Stalker July 12, 1949 2,489,683 Stalker Nov. 29, 1949 2,825,532 Kadosch et al Mar. 4, 1958 2,874,894 Goldschmied Feb. 24, 1959 FOREIGN PATENTS 586,010 Germany Oct. 14, 1953 754,055 Great Britain Aug. 1, 1956 758,906 Great Britain Oct. 10, 1956 780,464 Great Britain July 31, 1957 

